1. Field of the Invention
The present invention is related to a seamless capsule comprising a shell material encapsulating a center-filled core material, wherein the shell material is formed of a carbohydrate in glassy state, and a method and an apparatus for making the seamless capsule.
2. Description of the Prior Art
Traditionally, seamless capsules formed of a shell material encapsulating a core material have been made by using as the shell material film-forming materials such as gelatin and gums. These shell materials present two disadvantages. First, they are formed from an aqueous solution. Consequently, when the capsules are formed, large amounts of water must be removed, requiring great amounts of energy and long drying times. Second, these shell materials dissolve slowly when the capsules are being consumed, thereby leaving a distasteful plastic film-like residue in the mouth.
Seamless capsules are usually made by simultaneously extruding the shell material and the core material through concentrically aligned nozzles such that the extruded shell material and the extruded core material exit the nozzles as a coaxial jet with the shell material surrounding the core material into a stream of cooled carrier liquid that is flowing downward. While descending in the cooled carrier liquid, the coaxial jet breaks into droplets with the shell material encapsulating the core material. The droplets then solidify in the cooled carrier liquid to form seamless capsules. Such method is disclosed, for example, in U.S. Pat. Nos. 4,251,195 and 4,695,466. However, when the shell material is a material that solidifies quickly, this prior art method is disadvantageous in that the shell material in the coaxial jet may solidify prior to encapsulation. As a result, seamless capsules could not be formed, and any capsules that were formed were not spherical and did not have uniform size and shape.
An attempt to overcome this problem was proposed in U.S. Pat. No. 4,422,985, which describes a method that modifies the prior art method by introducing a coaxial triple jet consisting of a heated circulating liquid surrounding the shell material which in turn surrounds the core material into the cooled carrier liquid to allow encapsulation to take place. In this method, since capsule formation must still take place in the cooled carrier liquid, if any solidification of the shell material occurs prior to entering the cooled carrier liquid, encapsulation will not occur.
Other methods used for making capsules typically involve using a screw extruder to extrude an emulsion containing the shell matrix and the material to be encapsulated. However, in such process, it is difficult to make a capsule formed of a shell material encapsulating a center-filled core material. Instead, the encapsulated material is often in the form of globules that are distributed within the matrix.
U.S. Pat. No. 2,857,281 describes a process for making a solid flavoring composition in the form of globular particles by extruding an emulsion containing a sugar base and flavor oil into droplets.
U.S. Pat. No. 3,971,852, describes a process for encapsulating oil in a cellular matrix that is formed of polyhydroxy and polysaccharide compounds. The oil is in an emulsified state with the cellular matrix, and the resulting emulsion is spray dried as droplets of the emulsion.
U.S. Pat. No. 5,009,900 discloses a process for encapsulating volatile and/or labile components with extruded glassy matrices, wherein the encapsulated material is distributed in the glassy matrices.
European Patent Application No. 0339958 discloses an antifoaming composition containing an outer shell of a meltable sugar in its crystalline state with an organopolysiloxane antifoaming composition imbedded therein. This composition is formed by melting a sugar base and dispersing the organopolysiloxane antifoaming composition in the sugar melt as the discontinuous phase. The melt is then solidified, thereby imbedding and entrapping the antifoaming composition, which is dispersed in the melt.
U.S. Pat. No. 5,300,305 relates to microcapsules that provide long lasting breath protection.